1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that transfers a toner image to a printing medium.
2. Description of Related Art
For example, image forming apparatuses disclosed by Japanese Patent Laid-Open Publication No. 2005-258275 (Reference 1) and Japanese Patent Laid-Open Publication No. 2004-272144 (Reference 2) are well known. These image forming apparatuses are structured with an intension of preventing a printing medium from being stained with toner leaking out from a developing device. The image forming apparatuses disclosed by these documents are briefly described in the following.
The image forming apparatus disclosed by the Reference 1 has a structure to keep the inside of a developing device in a negative pressure. The image forming apparatus disclosed by the Reference 2 has a structure to prevent occurrence of an air flow from a developing device to the outside thereof. In the image forming apparatuses with the structures, toner leakage from the developing devices is suppressed.
Thus, the References 1 and 2 discuss suppression of toner leakage out from a developing device, while not discussing prevention of a printing medium from being stained with toner leaking out from a developing device.